Process for sterilization and production of fish meat paste product with use of microbubble and sterile fish meat paste product obtained by the process

ABSTRACT

This invention relates to a method of sterilizing and producing a fish-paste product by utilizing microbubbles, which comprises the steps consisting of adding ozone gas-containing microbubbles generated in water to raw materials of a fish-paste product, coating the interfaces of the ozone gas-containing microbubbles with tissues in raw materials of a fish-paste product thereby maintaining the longevity of the ozone gas-containing microbubbles, and stimulating the ozone gas-containing microbubbles thereby rupturing coating shells of the ozone gas-containing microbubbles, as well as a germ-free fish-paste product produced by the production method.

TECHNICAL FIELD

This invention relates to a method of sterilizing and producing afish-paste product by utilizing the sterilizing effect of ozonegas-containing microbubbles, as well as a germ-free fish-paste productproduced by the production method.

BACKGROUND ART

Heating sterilizing treatment, processing under aseptic conditions, etc.are carried out in production of fish-paste products because fish-pasteproducts are poor in an ability to keep for a long time and are subjectto growth of bacteria. However, the presence of thermostable bacteriaand inevitable and accidental contamination with bacteria areinevitable, so the fish-paste products suffer from problems such asdeterioration in the taste, influence on the health of the consumer,etc. and are kept under conditions made aseptic to a certain degree byadding an antiseptic and a preservative.

JP-A 57-33559 and JP-A 7-298855 propose a method of bleaching andsterilizing a fish-paste product with an organic acid, but the treatmentwith an organic acid has a problem of reduction in the qualities of thefish-paste product (reduction in elasticity, etc.).

DISCLOSURE OF INVENTION

The present invention was made under the circumstances described above,and the object of the invention is to provide a method of sterilizingand producing a fish-paste product by utilizing ozone gas-containingmicrobubbles, as well as a germ-free fish-paste product produced by theproduction method.

The object of the invention is achieved by the steps of adding ozonegas-containing microbubbles generated in water to raw materials of afish-paste product, coating the interfaces of the ozone gas-containingmicrobubbles with tissues in raw materials of a fish-paste productthereby maintaining the longevity of the ozone gas-containingmicrobubbles, and giving stimulation to a part of the ozonegas-containing microbubbles thereby rupturing coating shells of theozone gas-containing microbubbles.

The object of the invention is effectively achieved wherein the step ofadding the ozone gas-containing microbubble to raw materials of afish-paste product comprises adding water containing the ozonegas-containing microbubbles, or the step of adding the ozonegas-containing microbubbles to raw materials of a fish-paste productcomprises spraying a mist of water containing the ozone gas-containingmicrobubbles; the tissues are protein and lipid contained in thefish-paste product; the stimulation comprises rubbing together rawmaterials of the fish-paste product accompanying pestling of the rawmaterials, the stimulation comprises high-frequency irradiation of rawmaterials of the fish-paste product, the stimulation comprises microwaveirradiation of raw materials of the fish-paste product, or thestimulation comprises heating raw materials of the fish-paste product;or in the step of processing and packaging the fish-paste productfollowing the step of rupturing coating shells of the ozonegas-containing microbubbles, the packaged fish-paste product issubjected to the above stimulation to rupture coating shells of theozone gas-containing microbubbles contained in the fish-paste productthereby sterilizing the fish-paste product, or the object of theinvention is achieved by a germ-free fish-paste product maintaining anantibacterial ability obtained by the production method described above.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a scheme showing the method of sterilizing and producing afish-paste product by utilizing microbubbles.

BEST MODE FOR CARRYING OUT THE INVENTION

This invention relates to a method of sterilizing and producing afish-paste product by utilizing microbubbles, which comprises the stepsof adding ozone gas-containing microbubbles generated in water (referredto hereinafter as ozone gas-containing microbubbles) to raw materials ofa fish-paste product, coating the interfaces of the ozone gas-containingmicrobubbles with tissues in raw materials of a fish-paste productthereby maintaining the longevity of the ozone gas-containingmicrobubbles, and giving stimulation to a part of the ozonegas-containing microbubbles thereby rupturing coating shells of theozone gas-containing microbubbles, as well as a germ-free fish-pasteproduct produced by the production method.

Now, the properties (characteristics) of the microbubbles are describedin detail.

It is known that bubbles having a diameter of 50 μm or less(microbubbles) have properties different from those of usual bubbles.

The microbubbles have lower buoyancy than that of usual bubbles.Accordingly, the microbubbles are characterized by having a low rate ofclimb and a large surface area relative to their volume.

Hereinafter, the mode for carrying out the invention is described indetail by reference to the flow of FIG. 1. FIG. 1 is a scheme showingthe flow of the method of sterilizing and producing a fish-paste productby utilizing microbubbles according to the invention. The fish-pasteproduct refers to boiled fish paste, a tubular roll of boiled fishpaste, a light, puffy cake made of ground fish meat, a rolled omeletmixed with fish paste, tumire (one kind of fish paste), a deep-friedpatty of fish paste, boiled fish paste with bamboo grass, and naruto(one kind of fish paste).

First, ozone gas-containing microbubbles are provided water (S101). Anozone gas is contained in microbubbles whereby the sterilizing effect ofthe ozone gas can be effectively utilized.

Then, the ozone gas-containing microbubbles provided in S101 are addedto raw materials of a fish-paste product (S102). The method of addingthe ozone gas-containing microbubbles to raw materials of a fish-pasteproduct is not particularly limited, and is preferably a method whereinwater containing the ozone gas-containing microbubbles is added as suchto a fish-paste product or a method wherein water containing the ozonegas-containing microbubbles is sprayed in the form of a mist onto afish-paste product. The amount of the ozone gas-containing microbubblesadded to raw materials of a fish-paste product is not particularlylimited, but preferably the ozone gas-containing microbubbles are addedin an amount of 10 to 30 mL per g of the raw materials of a fish-pasteproduct.

The ozone gas-containing microbubbles are coated with tissues in rawmaterials of the fish-paste product (S103). As described above, thelongevity of microbubbles is known to be longer than that of usualbubbles, but the longevity of microbubbles cannot be maintained for afew hours or more, and thus the ozone gas-containing microbubbles shallbe coated with tissues in raw materials of the fish-paste product inorder to prevent disappearance of the ozone gas-containing microbubbles.Tissues in raw materials of the fish-paste product refer mainly toprotein and lipid. Coating of the microbubbles with protein and lipidoccurs for the following reason.

Among features of the microbubbles, the most remarkable feature is avery low rate of climb, and depending on the movement of water, themicrobubbles also move similarly to water. That is, the microbubblestend to behave as a complete mixture with water. This mixture contains alarge amount of the microbubbles, so its significantly excellentproperty lies in permeability into other material, thus permitting themixture to permeate very rapidly into raw materials of the fish-pasteproduct and into the fish-paste product itself. Because the water ismixed with protein and lipid in this permeation process, the protein andlipid having hydrophobic properties will inevitably aggregate in thegas/liquid interfaces of the microbubbles. As a result, coating shellsmade of the protein and lipid are formed around the microbubbles, andthe microbubbles having such coating shells are prevented fromshrinking. Accordingly, the longevity of the microbubbles issignificantly prolonged.

The longevity of the ozone gas-containing microbubbles, which is about120 seconds when the diameter is 10 μm, can be increased to 2-50 hoursby coating the ozone gas-containing microbubbles.

For rupturing the coating shells of a part of the ozone gas-containingmicrobubbles in the fish-paste product, the microbubbles are stimulated(S104) thereby rupturing the coating shells of the ozone gas-containingmicrobubbles (S105).

Because the coating shells of the ozone gas-containing microbubbles arestabilized by delicate balance, the ozone gas-containing microbubblesare ruptured one after another due to the influence of fluctuation inthe thermal motion of molecules in the fish-paste product etc. On onehand, the coating shells can be forcibly ruptured by giving physicalstimulation to the microbubbles.

By forcibly rupturing the coating shells by giving physical stimulationto the microbubbles, the ozone gas present in the microbubbles isreleased into surrounding tissues of the fish-paste product. This ozonegas is rapidly dissolved in tissues of the fish-paste product andsimultaneously converted by autolysis into oxygen, and in this process,the ozone gas transiently forms active oxygen species and free radicalspecies. These species are extremely highly aggressive to bacteria etc.and thus show an extremely excellent ability to sterilize raw materialsof the fish-paste product and the fish-paste product itself. The life ofactive oxygen species and free radical species is very short (severalmilliseconds or thereabout), and the whole of ozone is converted intooxygen harmless to foods.

Apart of the ozone gas-containing microbubbles contained in rawmaterials of the fish-paste product is stimulated to rupture coatingshells, so that even if the raw materials of the fish-paste product inthe stage of processing are contaminated with bacteria etc., thebacteria etc. are decomposed and the fish-paste product can besterilized by the sterilizing effect of the ozone gas.

The ozone gas-containing microbubbles contained in raw materials of thefish-paste product are not wholly ruptured but partially stimulated, sothat in the process of processing (production) of the fish-pasteproduct, the sterilizing effect can be continued and the re-stimulationof the fish-paste product for storage as described later can be carriedout.

The method of stimulating the ozone gas-containing microbubbles in thepresent invention is carried out preferably by rubbing together rawmaterials of a fish-paste product at the time of pestling the rawmaterials, by high-frequency irradiation or microwave irradiation of rawmaterials of a fish-paste product, or by heating raw materials of afish-paste product.

In the method of stimulating the microbubbles by rubbing together rawmaterials of a fish-paste product at the time of pestling the rawmaterials, the ozone gas-containing microbubbles contained in the rawmaterials of a fish-paste product are also rubbed together at the timeof pestling the raw materials of a fish-paste product. The effectivepestling rate for rupturing coating shells of the microbubbles ispreferably 10 to 20 cm/s, and the pestling time is preferably 20 to 60minutes.

The method of stimulating the microbubbles by high-frequency irradiationof raw materials of a fish-paste product is a method wherein coatingshells of the microbubbles are ruptured by utilizing the vibration ofmolecules in the raw materials of a fish-paste product upon stimulationof the microbubbles with high-frequency irradiation. The oscillationfrequency of the high frequency is preferably 30 to 50 kHz, and theirradiation time is preferably 2 to 10 minutes.

The method of stimulating the microbubbles by microwave irradiation ofraw materials of a fish-paste product is a method wherein coating shellsof the microbubbles are ruptured by utilizing the activation of thethermal motion of molecules in the raw materials of a fish-paste productupon stimulation of the microbubbles with microwave irradiation. Theoscillation frequency of the microwave is preferably 1500 to 3000 kHz,and the irradiation time is preferably 5 to 10 minutes.

The method of stimulating the microbubbles by heating raw materials of afish-paste product is a method wherein coating shells of themicrobubbles are ruptured by utilizing the vibration of molecules in theraw materials of a fish-paste product upon direct heating of the rawmaterials of a fish-paste product. Heating refers to steaming,deep-frying, baking, boiling, heating with Joule heat, etc. The heatingtemperature is preferably 50 to 80° C., and the heating time ispreferably 20 to 40 minutes.

As the method of stimulating the microbubbles as described above, asuitable method can be selected depending on the fish-paste product tobe produced.

The microbubbles whose coating shells are not ruptured will release anozone gas for a long time because the coating shells are graduallyruptured by the influence of thermal fluctuation in raw materials of afish-paste product upon stimulation or by their surrounding environmentetc.

The ozone gas-containing microbubbles contained in raw materials of afish-paste product are stimulated to rupture the coating shells, wherebythe raw materials of a fish-paste product are sterilized, and thesterilizing action is continued even in the process for producing afish-paste product. That is, the sterilizing effect is continuedthroughout a period of from the processing (production) of thefish-paste product (S106) to the packaging of the fish-paste product(S107).

The raw materials of the fish-paste product are stimulated to rupturethe coating shells, followed by the processing (production) of thefish-paste product (S106) and the packaging of the processed (produced)fish-paste product (S107).

The packaged fish-paste product is stimulated (S108), and the coatingshells of the ozone gas-containing microbubbles whose coating shells arestill not ruptured are ruptured (S109). By doing so, storage for a longtime can be achieved.

Stimulation in this stage is preferably high-frequency irradiation ormicrowave irradiation mentioned above because the fish-paste product hasbeen packaged. The oscillation frequency in high-frequency irradiationis preferably 30 to 50 Hz, the oscillation frequency in microwaveirradiation is preferably 1500 to 3000 Hz, and the irradiation time ispreferably 2 to 3 minutes.

If the coating shells of the microbubbles are not completely ruptured,the microbubbles whose coating shells are not ruptured will release anozone gas for a long time to continue sterilizing effect for a long timebecause the coating shells are ruptured one after another by theinfluence of thermal fluctuation in the raw materials of a fish-pasteproduct upon stimulation or by their surrounding environment etc.Accordingly, the decomposition of bacteria etc. due to rupture of thecoating shells of the microbubbles, and the sterilizing effect of theozone gas, can be continued for a prolonged period of time, thusproviding the fish-paste product having an antibacterial ability to theconsumer, which makes use of an antiseptic and a preservativeunnecessary thereby preventing deterioration in qualities of thefish-paste product and deterioration in the taste of the fish-pasteproduct and eliminating influence on the health of the consumer.

The method of sterilizing and producing a fish-paste product byutilizing microbubbles according to the present invention has beendescribed by reference to the flow shown in FIG. 1, but the presentinvention is not limited thereto. For example, after the step in S106 inthe present invention, the ozone gas-containing microbubbles may bestimulated (S108), followed by packaging the processed fish-pasteproduct.

In the step of stimulating a part of the microbubbles contained in theraw materials of the fish-paste product (S104), all the microbubblescontained in the raw materials of the fish-paste product may bestimulated to rupture the coating shells of the microbubbles. By doingso, the step of stimulating the microbubbles contained in the rawmaterials of the fish-paste product (S108) and the step of rupturing thecoating shells of the microbubbles (S109) can be omitted.

Hereinafter, the method of sterilizing and producing a fish-pasteproduct by utilizing microbubbles is illustrated by reference to theExamples.

EXAMPLES Example 1

0.5 L water containing ozone gas-containing microbubbles having anaverage bubble diameter of 15 μm at a density of at least 5000 bubblesper ml was added to 10 kg raw materials of a fish-paste product afterthawing, and within 20 seconds after addition, the raw materials weresubjected to pestling. Pestling was continued for 20 minutes duringwhich the relative speed of a pestle to a mortar was kept at 15 cm/s. Inthe raw materials, the number of general bacteria was 184600 /g, thenumber of Escherichia coli bacteria was 50 /g, the number ofStaphylococcus aureus bacteria was 650 /g, the number of Salmonellabacteria was 50 /g, Cereus bacteria were ++, and the number of Vibrioparahaemolyticus bacteria was 950 /g, but after pestling was carriedout, the number of any kind of the bacteria was 0 /g or below themeasuring range.

Example 2

10 kg raw materials of a fish-paste product after forming were sprayedwith a mist of 0.1 L water containing ozone gas-containing microbubbleshaving an average bubble diameter of 15 μm at a density of at least 5000bubbles per ml, and after spraying, were baked in a covered pan at 60°C. for 15 minutes. In the raw materials, the number of general bacteriawas 184600 /g, the number of Escherichia coli bacteria was 50 /g, thenumber of Staphylococcus aureus bacteria was 650 /g, the number ofSalmonella bacteria was 50 /g, Cereus bacteria were ++, and the numberof Vibrio parahaemolyticus bacteria was 950 /g, but after baking in acovered pan, the number of any kind of the bacteria was 0 /g or belowthe measuring range.

Example 3

10 kg raw materials of a fish-paste product after forming were sprayedwith a mist of 0.1 L water containing ozone gas-containing microbubbleshaving an average bubble diameter of 15 μm at a density of at least 5000bubbles per ml, and after spraying, the fish-paste product after formingwas irradiated with a high frequency with an oscillation frequency of 35kHz for 1 minute. The number of Cereus bacteria contained in the rawmaterials before irradiation with the high frequency was +, but afterirradiation with the high frequency, was below the measuring range.

Example 4

10 kg raw materials of a fish-paste product after forming were sprayedwith a mist of 0.1 L water containing ozone gas-containing microbubbleshaving an average bubble diameter of 15 μm at a density of at least 5000bubbles per ml, and after spraying, the fish-paste product after formingwas irradiated with a microwave with an output power of 1.5 kW and anoscillation frequency of 2000 kHz for 5 minutes. The number of Cereusbacteria contained in the raw materials before irradiation with themicrowave was +, but after irradiation with the microwave, was below themeasuring range.

Example 5

10 kg raw materials of a fish-paste product after heating treatment weresprayed with a mist of 0.05 L water containing ozone gas-containingmicrobubbles having an average bubble diameter of 15 μm at a density ofat least 5000 bubbles per ml, and after spraying, the fish-paste productwas packaged without adding a preservative. The fish-paste product afterpackaging was irradiated with a microwave with an output power of 1.5 kWand an oscillation frequency of 2000 kHz for 3 minutes, and a test ofstorage for 3 days in an atmosphere kept at a temperature of 30° C. wasconducted. As a result, the number of general bacteria in the fish-pasteproduct on the third day was 16150 /g, and the number of eitherEscherichia coli or Cereus bacteria was below the measuring range.

EFFECT OF THE INVENTION

The method of sterilizing and producing a fish-paste product byutilizing microbubbles according to the present invention can be used insterilizing raw materials of a fish-paste product, sterilizing them inthe process of producing a fish-paste product, making the final productgerm-free, and attaining a lasting effect of sterilization, and doesthus not require addition of an antiseptic or a preservative therebypreventing the deterioration in qualities of the fish-paste product andthe deterioration in the taste thereof caused by an antiseptic or apreservative and eliminating the influence of an antiseptic or apreservative if any on the health of the consumer.

INDUSTRIAL APPLICABILITY

The method of sterilizing and producing a fish-paste product byutilizing microbubbles according to the present invention can be used insterilizing raw materials of a fish-paste product, sterilizing them inthe process for producing a fish-paste product, making the final productgerm-free and achieving a lasting effect of sterilization, and isapplicable in food-related fields. According to the present invention,there can be provided foods not requiring addition of an antiseptic or apreservative, thus preventing the deterioration in qualities of thefish-paste product and the deterioration in the taste thereof caused byan antiseptic and a preservative and eliminating the influence of anantiseptic and a preservative if any on the health of the consumer.

1. A method for sterilizing and producing a fish-paste product byutilizing microbubbles comprising the steps of: adding ozonegas-containing microbubbles generated in water to raw materials of afish-paste product, coating the interfaces of the ozone gas-containingmicrobubbles with tissues in raw materials of the fish-paste productthereby maintaining the longevity of the ozone gas-containingmicrobubbles, and giving stimulation to a part of the ozonegas-containing microbubbles thereby rupturing coating shells of theozone gas-containing microbubbles.
 2. A germ-free fish-paste productmaintaining an antibacterial ability obtained by the sterilizingproduction method described in claim
 1. 3. A method according to claim1, wherein the step of adding the ozone gas-containing microbubbles toraw materials of the fish-paste product comprises adding watercontaining the ozone gas-containing microbubbles.
 4. (canceled)
 5. Amethod according to claim 1, wherein the step of adding ozonegas-containing microbubbles to raw materials of the fish-paste productcomprises spray a mist of water containing the ozone gas-containingmicrobubbles.
 6. (canceled)
 7. A method according to claim 1, whereinthe tissues are protein and lipid contained in the fish-paste product.8. (canceled)
 9. A method according to claim 1, wherein the stimulationcomprises rubbing together raw materials of the fish-paste products atthe time of pestling of the raw materials.
 10. (canceled)
 11. A methodaccording to claim 1, wherein the stimulation comprises high-frequencyirradiation of raw materials of the fish-paste product.
 12. (canceled)13. A method according to claim 1, wherein the stimulation comprisesmicrowave irradiation of raw materials of the fish-paste product. 14.(canceled)
 15. A method according to claim 1, wherein the stimulationcomprises heating raw materials of the fish-paste product. 16.(canceled)
 17. A method according to claim 1, wherein in the step ofprocessing and packaging the fish-paste product following the step ofrupturing coating shells of the ozone gas-containing microbubbles, thepackaged fish-paste product are subjected to the stimulation to rupturecoating shells of the ozone gas-containing microbubbles contained in thefish-paste products thereby sterilizing the fish-paste product. 18.(canceled)